This invention relates to copper articles with a surface capable of forming a cocontinuous bond, and methods and compositions of making the same.
It is an ongoing problem to bond organic materials to metal surfaces. When the bond between the metal surface and the organic material is exposed to heat delamination may occur. Delamination is the separation of the organic material which was bonded to the metal surface. Multilayer printed circuit boards (PCB""s) are typically constructed by interleaving imaged conductive layers, such as one containing copper with non-conductive layers such as a partially cured B-stage resin, i.e., a prepreg, into a multilayer sandwich which is then bonded together by applying heat and pressure. The conductive layer, e.g., copper circuitry, does not bond well to the non-conductive B-stage resin prepreg. Often intermediate layers are used to bond the B-stage prepreg to the copper circuitry.
To improve bonding, metal surfaces have been physically roughened to provide increased surface area for bonding. Also, the metal surfaces have been treated with chemicals to roughen the metal surface and improve adhesion. Metal oxide layers, such as immersion coatings of tin, have been placed on the surface of the metal to improve adhesion.
WO 9619097 relates to metal surfaces, usually copper, which are micro-roughened to improve adhesion of polymeric materials. The metal surfaces, usually copper, which are micro-roughened by use of an adhesion promoting composition comprising hydrogen peroxide, an inorganic acid, a corrosion inhibitor, such as a triazole, tettrazole, or imidazole.
This invention relates to a method of preparing a surface capable of making a cocontinuous bond comprising the steps of 1) obtaining a copper or copper alloy substrate and 2) applying an etching composition which comprises (a) an acid, (b) an oxidizing agent, (c) a copper complexing agent, and (d) a copper complex, wherein the copper complex is present in an amount which precipitates when applied to the copper or copper alloy substrate. The method also includes the step of 3) treating the substrate with a coating composition and/or 4) applying a stripping composition to the substrate. The invention also relates to copper articles, having surface with interconnected channels capable of forming a cocontinuous bond including multilayer articles such as printed circuit boards and compositions used in the method. The present invention provides a copper or copper alloy substrates which have improved adhesion properties to organic material.